sound wave
TRANSCRIPT
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Chapter 2
SoundSubject : Physics
Teacher : Piyanuch Plaon
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Sound
Energy is transferred from particle to particle through matter.
How we hear?
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Video about How we Hear?
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How we hear?
a. Outer ear collects sound.b. Middle ear amplifies sound.c. Inner ear converts sound.
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Longitudinal Wave (คลื่��นตามยาว)wave particles vibrate back and forth along the path that the wave travels.
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Transverse waves (คลื่��นตามขวาง)wave particles vibrate in an up-and-down motion.
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Parts of a Longitudinal
Wave
Compressions
Rarefactions
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Rarefactions (ส่�วนขยาย) are regions of low air pressure Compressions (ส่�วนอั�ด) are regions of high air pressure
Compressions
Rarefactions
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Sound Waves• Like other waves, a sound wave can be
described by its wavelength and frequency. • Wavelength is the distance from one
compression to another or one rarefaction to another.
• The frequency of a sound wave is the number of compressions or rarefactions that pass at a given point in one second.
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Sound waves also reflect, refract, diffract, and interfere.
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Propagation of sound
Medium (ต�วกลื่าง)- Material that sound waves can travel through.- It can travel through solids, liquids and gases but not through a vacuum.
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The Speed of Sound• The speed of sound is usually fastest in
solids, where molecules are closest together, and slowest in gases, where molecules are farthest apart.
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Speed of Sound
Depends on:1. Type of medium (ชน�ดขอังต�วกลื่าง)
- travels better through liquids and solids and gas can’t travel through a vacuum.
2. Temperature of medium (อั�ณหภู�ม�ขอังต�วกลื่าง)
- travels faster at higher temperature.
3. Density (ความหนาแน�น) - sound moves well through dense materials.
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Video about relation between amplitude and
frequency
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Intensity and loudness (ความเข�มเส่�ยง แลื่ะความด�ง)
1) Intensity depends on the energy in a sound wave.
2) Loudness is human perception of intensity.
3) Loudness is measured on the decibel scale.
Properties of sound
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Amplitude and Energy
• Sound waves with greater amplitude carry more energy and sound louder.
• Sound waves with smaller amplitude carry less energy and sound quieter.
• The higher the amplitude of the wave is, the more compressed the particles in the compression are and the more spread out they are in the rarefactions.
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Relation between amplitude and loudness
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- High frequency means more vibrations hitting the ear.- Pitch is how high or how low a sound seems to be.- Healthy humans can hear from 20 Hz to 20,000 Hz- We are most sensitive from 440 Hz to 7,000 Hz.
Frequency and pitch
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Relation between frequency and pitch
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- Ultrasonic sound has a frequency greater than
20,000 Hz.
a) Dogs (up to 35,000 Hz) b) Bats (over 100,000 Hz)
- Infrasonic sound has a frequency below 20 Hz
Frequency and pitch (Con.)
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Range of frequency
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